Ultrafast Scanning Probe Microscopy

We have combined the time resolution of short pulse laser techniques with the spatial resolution of the scanning tunneling microscope to image surfaces with 2 ps time resolution and 50 Å spatial resolution. Conventional short-pulse laser experiments have spatial resolution of a few μm due to the diffraction limit of optical beams. Scanned probe microscopes (SPM) have demonstrated spatial resolution better than 1Å, sufficient to resolve individual atoms, but time resolution is on the order of 1 ms for point measurements and 1 s for imaging, limited by the mechanical constraints of SPM scanners.